Locks, for example, combination locks are well known, and are widely used in various occasions to provide safety protection for goods and properties. At present there are many different types of portable locks available on the market, chiefly combination locks. One major drawback of prior and existing locks, however, is that a user may forget to lock the lock. This inherent problem in the usage of locks has not been adequately addressed by the prior art. Thus, it is desirable to provide a lock that includes an indicator that informs the user when the lock is left open or unlocked.